Laws: Fowler was difference
But Fowler, making his first City start of the season, scored three second-half goals to easy the Premiership side into the fourth round.
Laws said: "In the first hallf we were superb, deservedly 1-0 up and probably should have been 2-0.
"Stuart's aware that we went at them and matched them, second half in the first 15 minutes totally killed the game for us - they won the game in that 15 minute spell.
"They stepped the tempo up, and we gave the ball away a little bit cheaply.
"The penalty was harsh, he's been pulled down and landed on the ball."
Laws also singled out striker Fowler for praise, adding: "He is such an intelligent player, we were looking quite comfortable in the first-half and handling Robbie pretty well.
"I don't know why he has not been playing but he kept dropping into areas where our centre-halves did not want to be and we couldn't cope.
"We are a League One side and his knowledge and experience is bound to catch you out in the end."